What's the situation with ocular inflammation? A cross-seasonal investigation of proteomic changes in ocular allergy sufferers' tears in Victoria, Australia

Abstract

Background: Ocular allergy (OA) is a localized subset of allergy characterized by ocular surface itchiness, redness and inflammation. Inflammation and eye-rubbing, due to allergy-associated itch, are common in OA sufferers and may trigger changes to the ocular surface biochemistry. The primary aim of this study is to assess the differences in the human tear proteome between OA sufferers and Healthy Controls (HCs) across peak allergy season and off-peak season in Victoria, Australia.

Methods: 19 participants (14 OA sufferers, 5 HCs) aged 18-45 were recruited for this study. Participants were grouped based on allergy symptom assessment questionnaire scoring. Proteins were extracted from human tear samples and were run on an Orbitrap Mass Spectrometer. Peaks were matched to a DIA library. Data was analyzed using the software MaxQuant, Perseus and IBM SPSS.

Results: 1267 proteins were identified in tear samples of OA sufferers and HCs. 23 proteins were differentially expressed between peak allergy season OA suffers vs HCs, and 21 were differentially expressed in off-peak season. Decreased proteins in OA sufferers related to cell structure regulation, inflammatory regulation and antimicrobial regulation. In both seasons, OA sufferers were shown to have increased expression of proteins relating to inflammation, immune responses and cellular development.

Conclusion: Tear protein identification showed dysregulation of proteins involved in inflammation, immunity and cellular structures. Proteins relating to cellular structure may suggest a possible link between OA-associated itch and the subsequent ocular surface damage via eye-rubbing, while inflammatory and immune protein changes highlight potential diagnostic and therapeutic biomarkers of OA.

Keywords: allergic rhinoconjunctivitis; angiogenesis; human tears; inflammation; ocular allergy; protein biomarker; proteomics; wound healing.

Figure 1

The volcano plots show the significantly differentially expressed proteins between ocular allergy sufferers vs healthy controls after filtering out Log2 fold-changes on the x-axis of >1 or <-1; as well as by significance (p-value<0.05 was considered significant). (A) Volcano plot showing the difference in protein expression between peak allergy season ocular allergy sufferers vs healthy controls. All 14 proteins labelled in orange showed decreased expression in ocular allergy sufferers vs healthy controls during peak allergy season, while 9 proteins labelled in green showed increased expression. (B) Volcano plot showing the difference in protein expression between off-peak season ocular allergy sufferers vs healthy controls. All 13 proteins labelled in orange showed decreased expression in off-peak season between ocular allergy sufferers vs healthy controls, while 8 proteins labelled in green showed increased expression.

Figure 2

Summary of functions of each differentially expressed human tear protein between Ocular Allergy (OA) sufferers and Healthy Controls (HCs) across both seasons as determined by students t-test. Green protein ID’s are upregulated, while red are downregulated.

Figure 3

Boxplot of relative abundance of F-actin-capping protein subunit alpha (CAPZA1/2) expression in Ocular Allergy (OA) sufferers vs Healthy Controls (HCs) during peak allergy season and off-peak season. Stars (*) denote significantly different expression (p-value<0.05) between OA vs HCs.

Figure 4

Percentage of significantly up- and downregulated proteins associated with various biological processes as identified through functional analysis of human tear proteins in ocular allergy sufferers and healthy controls during (A) Peak allergy season and (B) Off-peak season.